1. Field of the Invention
The present invention relates to a dockboard apparatus having a particular mechanism for emplacement and storage of a ramp.
2. Description of the Prior Art
It is already known to use a dockboard having a movable ramp mounted in fixed supports on the vertical wall of a horizontal loading dock to facilitate the transfer of goods from the horizontal loading dock to an adjacent carrier, such as a truck or railroad car, having a horizontal bed or load surface of the same or nearly the same height as the fixed horizontal surface of the loading dock. U.S. Pat. No. 3,596,303 discloses a dockboard apparatus of the above-mentioned kind having a fixed support on the vertical wall, a chassis carried by the support in movable sliding relationship therewith, and a ramp pivotally mounted on the chassis for movement between a vertical storing position and a horizontal working position wherein it connects the two loading surfaces. The chassis is guided by elongated guide means which mesh with two guide means on the support. A counterbalancing device with a counterweight acts on the chassis.
In dockboard devices of the foregoing type there is a risk that the chassis will become skewed in relation to its guide means at least when the chassis is in its higher positions. In such positions much of the guide means on the chassis are above the guide means on the stationary support and thus are not fully effective in that only small portions of the guide means actually perform the guiding function. Furthermore, such arrangement of movable guide means is not satisfactory with, for example, regard to possible corroding or binding. With such design it is generally difficult to select the right materials and tolerances, and the long guide means are also susceptible to deformation.